It has been postulated that there are long-term effects of chronic exposure to marihuana, & that these long-term effects may be different or, perhaps, more drastic in individuals exposed to marihuana during early stages of development that at maturity. It is further hypothesized that the acute effects of marihuana depend upon the individual's prior experience with the drug and/or the prevaling environmental circumstances. The proposed research, then, is designed to provide an assessment of the acute and long-term psychobiologic effects of delta-9-tetrahydrocannabinol (THC) administered to pregnant rats. Fostering procedures will be introduced to distinguish between prenatal effects and effects attributable to postnatal maternal factors and maternal behavior will be continuously monitored. Similarly, control groups will be included to distinguish between the effects of "early" as opposed to "previous" drug exposure. The effects of THC will be assessed by measuring the development of behavioral arousal and neuroendocrine development (circadian rhythmicity, sexual maturation). Emotional and adrenocortical reactivity will be measured after treatment with THC and again at maturity. Learning will be assessed in a conditioned taste aversion paradigm and a competitive testing procedure will be used to assess dominance behavior and to reflect long-term retention of a taste aversion conditioned with THC. The immunologic competence of animals treated with THC will be assessed by measuring antibody production in response to immunogenic stimulation imposed upon animals under normal laboratory conditions, under conditions of stress, under stressful conditions wherein the animal is capable of coping with its environmemt, and under conditions manipulated to induce a "loss of control." Finally, the immunosuppressive effects of THC and the possibility of a THC-induced conditioned immunosuppression will be examined.